Jean-Philippe Brucker 2d21889f8b arm64: Don't insert a BTI instruction at inner labels ... Some ftrace features are broken since commit 714a8d02ca ("arm64: asm: Override SYM_FUNC_START when building the kernel with BTI"). For example the function_graph tracer: $ echo function_graph > /sys/kernel/debug/tracing/current_tracer [ 36.107016] WARNING: CPU: 0 PID: 115 at kernel/trace/ftrace.c:2691 ftrace_modify_all_code+0xc8/0x14c When ftrace_modify_graph_caller() attempts to write a branch at ftrace_graph_call, it finds the "BTI J" instruction inserted by SYM_INNER_LABEL() instead of a NOP, and aborts. It turns out we don't currently need the BTI landing pads inserted by SYM_INNER_LABEL: * ftrace_call and ftrace_graph_call are only used for runtime patching of the active tracer. The patched code is not reached from a branch. * install_el2_stub is reached from a CBZ instruction, which doesn't change PSTATE.BTYPE. * __guest_exit is reached from B instructions in the hyp-entry vectors, which aren't subject to BTI checks either. Remove the BTI annotation from SYM_INNER_LABEL. Fixes: 714a8d02ca ("arm64: asm: Override SYM_FUNC_START when building the kernel with BTI") Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Reviewed-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20200624112253.1602786-1-jean-philippe@linaro.org Signed-off-by: Will Deacon <will@kernel.org>		2020-06-24 14:24:29 +01:00
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asm	arm64: Don't insert a BTI instruction at inner labels	2020-06-24 14:24:29 +01:00
uapi/asm	arm64: Basic Branch Target Identification support	2020-03-16 17:19:48 +00:00